Correcting Someone's Grammar

My coworker consistently uses the word 'irregardless.' It makes her sound so ignorant, I can't help cringing. Is there a polite way to let her know about her mistake?

Unless you're her teacher, spouse, parent, or very good friend, don't correct her.

P.S. Put yourself in your colleague's shoes: If corrected, she'd probably feel embarrassed, which could lead to awkwardness between you. A caveat: If you're close or you're her boss, tell her privately, especially if her flub makes her look bad. (Try: "I used to do that, too, so I thought you'd want to know.")